127 lines
3.7 KiB
Java
127 lines
3.7 KiB
Java
package com.bytezone.diskbrowser.nufx;
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import com.bytezone.diskbrowser.utilities.Utility;
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// -----------------------------------------------------------------------------------//
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class LZW2 extends LZW
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// -----------------------------------------------------------------------------------//
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{
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private int nextEntry = 0x100;
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private String prev = "";
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private int codeWord;
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// ---------------------------------------------------------------------------------//
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public LZW2 (byte[] buffer, int crc, int eof)
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// ---------------------------------------------------------------------------------//
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{
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super (buffer);
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this.crc = crc;
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this.v3eof = eof;
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}
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// ---------------------------------------------------------------------------------//
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@Override
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void unpack ()
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// ---------------------------------------------------------------------------------//
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{
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crcBase = 0xFFFF;
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codeWord = 0;
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volume = buffer[0] & 0xFF;
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runLengthChar = (byte) (buffer[1] & 0xFF);
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int ptr = 2;
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while (ptr < buffer.length - 1)
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{
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int rleLength = Utility.getShort (buffer, ptr);
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boolean lzwPerformed = (rleLength & 0x8000) != 0;
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ptr += 2;
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if (lzwPerformed)
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{
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rleLength &= 0x0FFF; // remove the LZW flag
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if (rleLength == 0)
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rleLength = TRACK_LENGTH;
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int chunkLength = Utility.getShort (buffer, ptr);
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ptr += 2;
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setBuffer (ptr); // prepare to read n-bit integers
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byte[] lzwBuffer = undoLZW (rleLength);
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if ((chunkLength - 4) != bytesRead ())
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System.out.printf ("Invalid chunk length%n");
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if (rleLength == TRACK_LENGTH) // no run length encoding
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chunks.add (lzwBuffer);
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else
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chunks.add (undoRLE (lzwBuffer, 0, lzwBuffer.length));
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ptr += bytesRead (); // since the setBuffer()
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}
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else
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{
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nextEntry = 0x100;
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if (rleLength == 0)
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rleLength = TRACK_LENGTH;
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if (rleLength == TRACK_LENGTH) // no run length encoding
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{
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byte[] originalBuffer = new byte[TRACK_LENGTH];
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System.arraycopy (buffer, ptr, originalBuffer, 0, originalBuffer.length);
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chunks.add (originalBuffer);
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}
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else
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chunks.add (undoRLE (buffer, ptr, rleLength));
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ptr += rleLength;
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}
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}
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}
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// ---------------------------------------------------------------------------------//
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byte[] undoLZW (int rleLength)
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// ---------------------------------------------------------------------------------//
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{
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byte[] lzwBuffer = new byte[rleLength]; // must fill this array from buffer
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int ptr = 0;
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while (ptr < rleLength)
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{
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codeWord = readInt (width (nextEntry + 1));
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if (codeWord == 0x100) // clear the table
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{
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nextEntry = 0x100;
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codeWord = readInt (9);
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prev = "";
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}
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String s = (nextEntry == codeWord) ? prev + prev.charAt (0) : st[codeWord];
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if (nextEntry < st.length)
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st[nextEntry++] = prev + s.charAt (0);
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for (int i = 0; i < s.length (); i++)
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lzwBuffer[ptr++] = (byte) s.charAt (i);
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prev = s;
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}
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return lzwBuffer;
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}
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// ---------------------------------------------------------------------------------//
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@Override
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public String toString ()
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// ---------------------------------------------------------------------------------//
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{
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StringBuilder text = new StringBuilder ();
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text.append (String.format (" volume ............ %,d%n", volume));
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text.append (String.format (" RLE char .......... $%02X", runLengthChar));
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return text.toString ();
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}
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} |